Control of admixture action in concrete and other materials is limited by the methods and timing of delivery. Admixtures are most often added at time of mixing, which is not necessarily optimal for the desired chemical effects. For instance, it is sometime desirable to delay release of compounds such as superplasticizers, retarders, accelerators, and other additives.
The prior art describes “encapsulation” procedures for delivery of chemicals. Such procedures often rely on mechanisms involving dissolution (coating), diffusion (membranes), desorption (porous materials), and mechanical dispersion (during mixing), which are expensive and time-consuming.
Pronounced anion exchange capacity of LDHs and LDH-like materials makes interlamellar ion exchange by organic and inorganic anions versatile and easy. LDHs have been investigated extensively in a wide range of applications such as catalysts, ceramic precursors, adsorbents, bio-organic nanohybrids, and also as scavengers of pollutant metals and anions. Recent research has shown great flexibility of the anionic clays in tailoring chemical and physical properties of materials to be used for specific application, e.g. molecular recognition, optical storage, batteries, etc. Furthermore, by introducing various transition and noble metals into the sheets of the LDH structure, researchers have been able to produce catalyst precursors. More recently, there have been a tremendous number of new developments using a LDH as a matrix for storage and delivery of biomedical molecules and as a gene carrier.
Development of new inexpensive materials for programmed delivery and action control of admixtures in cement-based compositions would present a significant technological advance.